1. Field of the Invention
The invention relates to insulative electrical connectors for conductors and more particularly concerns heat sealable, synthetic polymer resin sleeves or tubes which may be slipped over an electrical connection and fused to the connection.
2. Brief Description of the Prior Art
Prior hereto, sleeves of heat shrinkable materials have been employed to enclose electrical conductors and connections; see for example U.S. Pat. No. 2,027,962. Heat shrinkable sleeves have also been employed for this purpose, which include fusable liners to assist in sealing the sleeve to the conductors or their insulative coverings; see for example U.S. Pat. Nos. 3,243,211; 3,582,457; and 3,814,139.
The present invention is an improvement over the prior art heat shrinkable tubes and processes. First, the sheaths of the present invention may be, and in fact preferably are fabricated from heat-shrinkable polymeric resin material but this is not a necessity as is the case in the prior art. Indeed, the sheath may be constructed according to the invention with non-shrinkable materials, lending greater versatility to their applications where materials of greater rigidity and/or dimensional stability are desired. Consequently, the process of the invention is also advantageous since it is not dependent upon exposing a heat-shrinkable tube to a specific heat-shrinking temperature. Secondly, the prior art sleeves had to be provided in a variety of different diameters because a different sleeve was needed for each of the various conductors and connections of differing gauge. This was necessitated by the more critical need to approximate the diameter or size of the conductor to be covered. A large inventory of sleeves of differing dimension was required to accomplish this. Because the sheaths of the present invention are adaptable to installation on a wider variety of gauges, fewer sizes are required and smaller inventories are required to be maintained. This is a significant economical advantage.
Further, the sheaths and process of the invention insulate the electrical conductors and connections by encapsulating them in a matrix of a polymeric resin foam. This advantageously improves the physical strength of the electrical connection as well as improving the quality of protection afforded to the electrical conductor or connection for which protection is sought. More specifically, an electrical conductor or connection encapsulated in a polymeric resin foam according to the invention has improved dielectric properties in that substitution of a gas for part of the conventional solid polymer insulation results in lowered dielectric constant, dissipation factor and increased dielectric strength. This is particularly advantageous for low frequency electrical systems where it is desirable to make the dielectric constant of insulative material as low as possible. In high-frequency systems the lowered dissipation factor is highly advantageous.
Encapsulation of the electrical conductor or connection in a closed cell polymer resin foam protects the conductor and/or connection from the weather, humidity, galvanic action (particularly where the connection is between diverse metals) adverse thermal conditions (the foam is heat-insulative) rot, mildew, flex fatigue and the like. The foam also serves to cushion the connection, providing more flexible connections and shock absorbing connections. Fire resistant foam formulations may be used to give the electrical connections greater protection against open flame.